The present invention relates to cranes for lifting loads, more particularly, to a rotary tower crane which eliminates the need for winches, cable, line and hoisting tackle.
Rotary tower cranes have long been utilized on construction sites to lift steel, concrete, large tools, and generators. A typical tower crane comprises a base bolted to a large concrete pad which supports a vertical steel framework tower that can be extended in sections. Attached to the top of the tower is a slewing unit including a ring gear and a motor for rotating a long horizontal jib or working arm which carries the load lifted by the crane. A shorter horizontal counterjib or machinery arm connects to the rear end of the jib and carries a large counterweight or ballast. A trolley runs along the jib and positions a hoisting cable or rope. An operator sitting in a cab, just below the inner end of the jib, manipulates controls for moving the jib to a preselected angular location, moving the trolley to place the hoisting cable at a predetermined radial location, and for operating the winch to raise and lower the hoisting tackle. Typically the operator works in conjunction with construction crew who manually connect and disconnect the hoisting tackle to and from a given load. Therefore, in most instances, precision location of the hoisting tackle and/or the load carried thereby, is not required.
There are some situations in which it would be desirable for the operator of a tower crane to be able to handle loads without the assistance of a member of the construction crew. This is very difficult to accomplish if a lifting cable or line is utilized due to its inherent tendency to twist and swing and therefore the hoisting tackle is difficult to correctly position. Furthermore, conventional hoisting tackle typically includes a hook, a shackle, and other means of attachment that must be manually connected to, and disconnected from, the load at the load lifting and load depositing areas, respectively, of the construction site. One such situation involves a toy tower crane that is remotely manipulated by a player through hard wired or radio control.
Therefore, it is the primary object of the present invention, to provide an improved crane.
It is another object of the present invention to provide an improved rotary tower crane.
It is still another object of the present invention to provide a generic boom extender module that may be used in a crane, and in other environments where it is desirable to provide bilinear actuation.
Still another object of the present invention is to provide a radio-controlled toy tower crane particularly adapted for use in a simulated miniature construction site or industrial environment.
In accordance with the present invention, a crane has a jib that extends in a horizontal direction and a trolley movable along the jib in a longitudinal direction. A first drive unit moves the trolley to a selected longitudinal direction along the jib, a second drive unit mounted on the trolley extends and retracts a rigid load maneuvering boom in a vertical direction. A load handler is mounted to the lower end of the boom.
In accordance with the present invention, a tower crane has a jib that extends in a horizontal direction. A counterjib extends in a horizontal direction and is connected to the jib. The jib and counterjib are supported by a stewing unit mounted to the upper end of the tower for powered rotation of the jib and the counterjib about a vertical axis. A first electrical drive unit powers the stewing unit to rotate the jib to a selected angular position relative to the tower. A trolley is movable along the jib. A second electrical drive unit powers the trolley to a selected longitudinal position along the jib. A third electrical drive unit mounted on the trolley extends and retracts a load lifting boom along a vertical direction. A load handler is mounted to a lower end of the boom.
The present invention also provides a boom extender module that includes an elongate guide sleeve having an opening in a sidewall thereof. A frame is mounted to the guide sleeve adjacent to the opening. A cog is rotatably supported on the frame so that the teeth of the cog penetrate the opening in the guide sleeve.